The present invention relates generally to chambers, and more particularly, to substrate transport chambers and methods of efficiently manufacturing the same.
Transport modules are generally used in conjunction with a variety of substrate processing modules, which may include semiconductor processing systems, material deposition systems, and flat panel display processing systems. Due to the growing demands for cleanliness and high processing precision, there has been a growing need to reduce the amount of human interaction between processing steps. This need has been partially met with the implementation of transport modules which operate as an intermediate handling apparatus (typically maintained at a reduced pressure, e.g., vacuum conditions). By way of example, a transport module may be physically located between one or more clean room storage facilities where substrates are stored, and multiple substrate processing modules where the substrates are actually processed, e.g., etched or have deposition performed thereon.
In this manner, when a substrate is required for processing, a robot arm located within the transport module may be employed to retrieve a selected substrate from storage and place it into one of the multiple processing modules. As is well known to those skilled in the art, the use of a transport module to "transport" substrates among multiple storage facilities and processing modules is typically referred to as a "cluster tool architecture."
FIG. 1 depicts a typical cluster tool architecture 100 illustrating the various chambers that interface with a transport module 106. Transport module 106 is shown coupled to three processing modules 108a-108c which may be individually optimized to perform various fabrication processes. By way of example, processing modules 108a-108c may be implemented to perform transformer coupled plasma (TCP) substrate etching, layer depositions, and sputtering. There may be connected to transport module 106 a load lock 104, through which substrates may be provided to transport module 106.
As illustrated, load lock 104 is coupled to a clean room 102 where substrates may be stored. In addition to being a retrieving and serving mechanism, load lock 104 also serves as a pressure varying interface between transport module 106 and clean room 102. Therefore, transport module 106 may be kept at a constant pressure (e.g., vacuum), while clean room 102 is kept at atmospheric pressure.
As the demand for larger substrates increases, the need for transport modules capable of transporting these larger substrates also increases. Consequently, as the need for physically larger transport modules increases, existing manufactures of off-the-shelf transport modules have been struggling to develop larger transport modules in a cost effective manner. Unfortunately, existing methods of making these larger transport modules have proved to be extremely inefficient and prohibitively expensive to manufacture. For illustration purposes, the following will illustrate two common methods of manufacturing a transport chamber, which may represent, in one case, the transport module without the electronics.
FIG. 2A is a simplified transport chamber 200 assembled using conventional weldment technology. By way of example, transport chambers made by weldment technology generally require machined flat metal plates which are welded together to form boxed enclosures. As illustrated, transport chamber 200 is assembled into a box configuration 202 having four metal plate sides 204, and a bottom plate 206 welded together at linear intersections 208. Interface ports 210 will generally be required to form a path for the substrates to be transported into and out of transport chamber 200, and may be machined out before or after box 202 has been welded together. A top plate (not shown) may then be designed to fit over the top perimeter of side plates 204. In this manner, a seal may be formed when the top plate is welded or bolted down to box 202. If the top plate is bolted down, an O-ring seal is typically placed between the top plate and the top surface regions of side plates 204 before being bolted down to box 202.
As can be appreciated, the welding process may be very labor intensive in that the weld must be uniform and provide a vacuum-tight seal where the various plates meet. In addition, large amounts of machining time may be spent in preparing the various plates in order to generate smooth meeting surfaces for subsequent welding steps. By way of example, plates 204 must be precisely machined to smoothly match bottom plate 206. In this manner, less time is consumed adjusting plates that fail to meet up with each other. Finally, once box 202 has been welded together, additional time must be spent performing post-weldment machining to cure any heat generated warping that may have been introduced during the welding process. As is well known in the art, the intensity of the thermal heat introduced during a welding process may tend to cause extensive distortions that further increase the time and expenses associated with post-weldment machining processes used to face-off warped regions.
One disadvantage associated with a weldment-type transport chamber 200 is that it may have structural deficiencies due to the vast amount of linear inches requiring welding. For illustration purposes, relatively long regions of welding are required for large transport chambers having dimensions between 60 and 100 inches. The structural weakness introduced at welding interfaces therefore produces well known step-down regions. By way of example, if a welding interface were magnified and examined closely, a thinner plate dimension would result at weld interfaces. Therefore, in order to prevent the introduction of structural weaknesses, more time and expense must be invested to assure that typical loads up to about 75,000 pounds are withstood. Further, welded structures may cause failures associated with long term fatigue.
In addition, once all post weldment machining is complete, additional cleaning steps must be performed to remove any surface metal contamination introduced during welding. Consequently, further time, effort and expense must be invested in cleaning the finished transport chamber before being spun into operation.
FIG. 2B illustrates another conventional manufacturing process used to make transport chamber 250. The manufacturing process is sometimes referred to as a "hogout" process since transport chamber 250 is formed from an initial solid billet 254 of aluminum. Solid billet 254 is typically machined-out from one side in order to generate a hollow region in the center (e.g., thereby forming a box similar to that of FIG. 2A). A hogout transport chamber does provide certain advantages over weldment-type transport chambers, but other disadvantages are introduced. By way of example, the machining required to define a hollow region 256 in a large billet of aluminum tends to be very labor-intensive, and the machining process also tends to generate large quantities of unusable aluminum scraps.
Once the machining process is complete, hollow region 256 must be polished down to produce smooth sides and eliminate any contaminating materials or scrap. A top plate may then be designed to fit over the box structure generated from the machining process. Next, interface ports 258 are defined to provide the passageways for substrates to be introduced into and out of transport chamber 250.
In addition to being a very labor intensive process, generating transport chamber 250 from solid billet 254 is very expensive. As can be appreciated, solid billet 254 is remarkably heavy and must be paid for by the pound. Therefore, once the scrap is machined out, about 80 percent of the aluminum is wasted since industry does not pay well for recycled scraps.
There are entities that provide ready-made transport chambers of the weldment type and hogout type. By way of example, Brooks Automation of Lowell, Mass. is a supplier of ready-made chambers. Although there are companies that make custom transport chambers, the traditional method used to build weldment type or hogout type chambers is typically very expensive.
In view of the forgoing, what is needed is a transport chamber that employs a cost efficient manufacturing method for generating large transport chambers, without producing warping and structural deficiencies of a weldment, and without expending large amounts of time machining hollow regions in large solid billets which produce useless waste.